HMS K4 (Cdr B de B Stocks) sailed from Rosyth as part of the 12th Submarine Flotilla on 31 January 1918 and became involved in what has become known as The Battle of May Island. The vessels involved sailed in the order HMS FEARLESS (cruiser), HMS K4, K3, K6, K7, K12 and K17.

K17 crossed FEARLESS bows from port to starboard and, despite ordering full astern, FEARLESS collided with and sank K17. K4, on hearing the cruiser give three blasts for full astern, came to a stop. K3, (Lt Cdr H W Shove), the next in line, avoided K4 and came to a stop 500 yards further on. K6, having taken avoiding action to miss K12, ploughed into K4, almost slicing her in half.

K7 also went full astern, and, although narrowly avoiding K6, ran over the sinking K4. There were no survivors.